DESCRIPTION (Verbatim from the application): HIF- 1a is a central mediator of hypoxia-induced alterations in gene transcription and is likely to play a prominent role in hypoxic signaling in cardiac myocytes. Using cre-lox based conditional gene targeting we have generated viable mice with cardiac myocyte specific homozygous deletion of HIF-l a. Our initial findings have documented changes in cardiac morphotnetry, diastolic function, expression of glucose transporters, and responses to physiologic cardiac stress in these mice. These findings establish that homozygous deletion of HIF-1alpha in cardiac myocytes is not fully compensated by complimentary hypoxic signaling mechanisms. These mice present a unique and powerful model system to study the role of hypoxic signaling in cardiac adaptive responses to hypoxia/ischemia and hemodynamic stress. We will use these mice to study the role of HIF-1alpha in cardiac glucose metabolism, contractile function, angiogenesis, and adaptation to pressure overload and chronic hypoxia. We have also developed adenovirus vectors that force overexpression of HIF-la. We have shown these vectors capable of transcriptionally activating HIF1alpha responsive genes, and have discovered that augmented HIF-1alpha signaling results in a decrease of SERCA2 transcripts; a finding that may have implications regarding the effects of hypoxia/ischemia on cardiac contractile function. In this proposal we will further delineate the specific role of HIF-1alpha dependent signaling in the cardiac myocyte and fulfill the following aims: 1) Determine the role of cardiac myocyte specific HIF-1alpha dependent signaling in metabolic, morphometric and functional adaptation to hypoxia and pressure overload. 2) Determine the role of cardiac myocyte specific HIF-1alpha dependent signaling in paracrine mediation of angiogenesis in adaptation to hypoxia and pressure overload. 3) Determine the role of cardiac myocyte specific HIF-1alpha dependent signaling in myocyte survival and apoptosis pathways.